Clock



FIG. 1 is a front elevation of a clock showing my new design;

FIG. 2 is a rear elevation thereof;

FIG. 3 is a left side elevation thereof;

FIG. 4 is a top plan view;

FIG. 5 is a bottom plan view; and,

FIG. 6 is a top, front and right side perspective view thereof. 

The ornamental design for a clock, as shown and described. 